Multiple Forms of “Kiss-and-Run” Exocytosis Revealed by Evanescent Wave Microscopy

Henry Wellcome Laboratories for Integrated Cell Signalling and Department of Biochemistry, School of Medical Sciences, University Walk, University of Bristol, BS8 1TD, Bristol, United Kingdom.
Current Biology (Impact Factor: 9.57). 05/2003; 13(7):563-7. DOI: 10.1016/S0960-9822(03)00176-3
Source: PubMed


Exocytotic release of neuropeptides and hormones is generally believed to involve the complete merger of the secretory vesicle with the plasma membrane. However, recent data have suggested that "kiss-and-run" mechanisms may also play a role. Here, we have examined the dynamics of exocytosis in pancreatic MIN6 beta cells by imaging lumen- (neuropeptide Y/pH-insensitive yellow fluorescent protein; NPY.Venus) or vesicle membrane-targeted fluorescent probes (synaptobrevin-2/enhanced green fluorescent protein; synapto.pHluorin, or phosphatase on the granule of insulinoma-enhanced green fluorescent protein, phogrin.EGFP) by evanescent wave microscopy. Unexpectedly, NPY.Venus release events occurred much less frequently (13%-40% maximal rate) than those of synapto.pHluorin, even though the latter molecule, but not phogrin.EGFP, usually diffused away from the site of fusion. Thus, the majority of exocytosis occurs in these cells by kiss-and-run events that involve either the release of small molecules only, small molecules and selected membrane proteins, or all soluble cargoes ("pure," "mixed," and "full" kiss-and-run, respectively). Changes in the activity of synaptotagmin IV, achieved here by overexpression of the wild-type protein, may allow different stimuli to alter the ratio of these events, and thus the release of selected vesicle cargoes.

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    • "In this review, we discussed the application of the technique to visualize deformations occurring before the fusion event, and later, during fusion pore expansion. Recent work supports the idea that events associated with the fusion pore can take distinct pathways (Taraska et al. 2003; Tsuboi and Rutter 2003; Perrais et al. 2004; Fulop et al. 2005). This has important implications for the extent to which plasma membrane morphology is reordered upon fusion. "
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